The ability to distribute limited mental resources among tasks or stimuli and to efficiently shift the "internal spotlight" of attention is critical to adaptive functioning in a demanding and complicated world. The prefrontal regions of the human brain are critical for multiplexing attention, which is frequently impaired in neurological and neuropsychiatric conditions associated with frontal pathology. Current static "frontal executive system" task derived from traditional paper and pencil neuropsychological tests have a number of limitations, foremost the inability to adapt in difficulty and provide a consistently challenging level across subjects with varying ability. This project aims to develop a dynamic, adaptive attention switching "stress test," the Multiplexing Test (MT), to address the need for a modern test of this essential cognitive function. As a research and clinical assessment instrument used with or without brain function monitoring, the MT could serve as a standardized activation procedure for testing patients whose attentional multiplexing abilities might be diminished due to illness, medication side-effects or advancing age, and as an outcome measure in treatment efforts to ameliorate cognitive impairments. Building on the achievements of projects that developed the MT for young adults and children, in Phase I we pilot tested and refined the MT for use with elderly subjects, and then applied it to 22 new subjects with and without mild cognitive complaints. The results demonstrated that the MT is suitable for this population, producing highly reliable task performance and associated EEG and evoked potential data comparable to data from younger subjects, yet differed between elderly subjects with and without objective signs of mild executive dysfunction. The results provide strong support for the scientific and technical feasibility of the MT as an executive brain function test applicable across the life span. In Phase II we plan to extend and further validate the MT on a healthy normative population of middle-aged and elderly adults and on patients with disorders producing mild executive impairment, integrate the MT with our automated cognitive neurophysiological EEG testing system, and subject it to independent evaluation by collaborators. The data collected from these studies will be used to determine the test's psychometric properties in this population and its suitability for evaluating the effects on attentional multiplexing of normal aging and several common disorders that affect middle age and elderly people, including multiple sclerosis, obstructive sleep apnea and Mild Cognitive Impairment (MCI). The MT will also be used in a collaborative pilot fMRI study, and MT performance plus EEG results will be compared with FDG PET scans in a subset of the MCI patients. PUBLIC HEALTH RELEVANCE: The ability to efficiently switch attention is critical to functioning in today's complex world, and many diseases like dementia impair it. Surprisingly, there is no modern test of this fundamental cognitive function. The Multiplexing Test (MT) is a next-generation dynamic and adaptive test of attention switching that is applicable across the lifespan from 6 to 90+ years of age. The MT is designed for simultaneous measurement of brain function with EEG, fMRI or PET for improved research and patient care. In addition to commercializing the MT as an essential part of the SAM Exam automated, high-throughput, clinical neurophysiological testing system, The MT will also be made available as a stand-alone test at no charge to Federally funded cognitive neuroscience researchers.